PIC24FJ64GA705 Datasheet, PDF (114/412 Pages) –

PIC24FJ256GA705 FAMILY
10.2.2 IDLE MODE
Idle mode has these features:
• The CPU will stop executing instructions.
• The WDT is automatically cleared.
• The system clock source remains active. By
default, all peripheral modules continue to operate
normally from the system clock source, but can
also be selectively disabled (see Section 10.4
“Selective Peripheral Module Control”).
• If the WDT or FSCM is enabled, the LPRC will
also remain active.
The device will wake from Idle mode on any of these
events:
• Any interrupt that is individually enabled.
• Any device Reset.
• A WDT time-out.
On wake-up from Idle, the clock is reapplied to the CPU
and instruction execution begins immediately, starting
with the instruction following the PWRSAV instruction or
the first instruction in the ISR.
10.2.3
INTERRUPTS COINCIDENT WITH
POWER SAVE INSTRUCTIONS
Any interrupt that coincides with the execution of a
PWRSAV instruction will be held off until entry into
Sleep or Idle mode has completed. The device will
then wake-up from Sleep or Idle mode.
10.2.4
LOW-VOLTAGE RETENTION
REGULATOR
PIC24FJ256GA705 family devices incorporate a
second on-chip voltage regulator, designed to provide
power to select microcontroller features at 1.2V nomi-
nal. This regulator allows features, such as data RAM
and the WDT, to be maintained in power-saving modes
where they would otherwise be inactive, or maintain
them at a lower power than would otherwise be the
case.
Retention Sleep uses less power than standard Sleep
mode, but takes more time to recover and begin execu-
tion. An additional 10-15 µS (typical) is required to
charge VCAP from 1.2V to 1.8V and start to execute
instructions when exiting Retention Sleep.
The VREGS bit allows control of speed to exit from the
Sleep modes (regular and Retention) at the cost of
more power. The regulator band gaps are enabled,
which increases the current but reduces time to recover
from Sleep by ~10 µs.
The low-voltage retention regulator is only available
when Sleep mode is invoked. It is controlled by the
LPCFG Configuration bit (FPOR<2>) and in firmware
by the RETEN bit (RCON<12>). LPCFG must be pro-
grammed (= 0) and the RETEN bit must be set (= 1) for
the regulator to be enabled.
10.2.5
EXITING FROM LOW-VOLTAGE
RETENTION SLEEP
All of the methods for exiting from standard Sleep also
apply to Retention Sleep (MCLR, INT0, etc.). However,
in order to allow the regulator to switch from 1.8V (oper-
ating) to Retention mode (1.2V), there is a hardware
‘lockout timer’ from the execution of Retention Sleep
until Retention Sleep can be exited.
During the ‘lockout time’, the only method to exit Reten-
tion Sleep is a POR or MCLR. Interrupts that are
asserted (such as INT0) during the ‘lockout time’ are
masked. The lockout timer then sets a minimum interval
from when the part enters Retention Sleep until it can exit
from Retention Sleep. Interrupts are not ‘held pending’
during lockout; they are masked and in order to exit after
the lockout expires, the exiting source must assert after
the lockout time.
The lockout timer is derived from the LPRC clock,
which has a wide (untrimmed) frequency tolerance.
The lockout time will be one of the following two cases:
• If the LPRC was not running at the time of
Retention Sleep, the lockout time is
2 LPRC periods + LPRC wake-up time
• If the LPRC was running at the time of Retention
Sleep, the lockout time is 1 LPRC period
Refer to Table 32-20 and Table 32-21 in the AC Electrical
Specifications for the LPRC timing.
10.2.6
SUMMARY OF LOW-POWER SLEEP
MODES
The RETEN bit and the VREGS bit (RCON<12,8>)
allow for four different Sleep modes, which will vary by
wake-up time and power consumption. Refer to
Table 10-1 for a summary of these modes. Specific
information about the current consumption and
wake times can be found in Section 32.0 “Electrical
Characteristics”.
TABLE 10-1: LOW-POWER SLEEP MODES
RETEN VREGS
MODE
Relative Power
(1 = Lowest)
0
0
Sleep
3
0
1
Fast Wake-up
4
1
0
Retention Sleep
1
1
1
Fast Retention
2
DS30010118B-page 114
 2016 Microchip Technology Inc.